The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In order to carry out resistant and lightweight structural elements, particularly in the aeronautical field, it is known to prepare a textile preform from dry fibers, in particular carbon fibers, which is then impregnated with a resin in a tooling, following a method called “LCM” (Liquid Composite Molding) method.
The fluid resin here carries out a complete impregnation of the preform, and the tooling allows a shaping of this assembly. After curing to polymerize the resin, there is obtained an element comprising fibers whose density and orientation are adjusted in order to obtain high mechanical resistance characteristics, adapted to the forces applied to this part.
Particularly, it is possible to produce parts including an elongated shape along a longitudinal direction, having an evolutive variable transverse section.
For example, a rear frame of a thrust reverser cascade for a turbojet engine constitutes an elongated part comprising a constant flat section forming substantially a belt, having at each end its two lateral flanges folded so as to form a yoke including two parallel wings. A transverse drilling of the wings receives an axis allowing, in the longitudinal direction, a clamping traction on the ends.
In the case of an elongated part having a flat section which, in the length, changes the plane to reach 90°, a known solution consists in flat-draping two-dimensional fabric plies, then in deforming this assembly by twisting it along a quarter turn to carry out progressively the change of plane.
However, for this solution, the cutting and the manipulation of a multitude of narrow and slender fabric plies can cause problems of losses of wicks at the edge of plies, and of significant deformations of these plies. In addition, the deformation of the plies can also lead to local disorientations of the fibers, which are not controllable if they are inside the part.
Moreover, the dimensions of such a part with finished sides leaving the molding are difficult to obtain, and in most cases, it is necessary to carry out a machining after the polymerization, which is expensive.
Another solution for carrying out a change of section consists in manufacturing a multi-layer preform of a ribbon type, then in increasing the number of layers locally and progressively by a successive addition of warp and weft yarns.
There is thus obtained a single preform including a local thickening where warp yarns are added successively. However, the absence of continuity of these added yarns greatly reduces the mechanical strength of the assembly, in the areas of variation of the number of yarns.